1. Field of the Invention
The genus Diabrotica comprises many of the economically important field pests afflicting U.S. agriculture. In the adult stage the diabroticites are responsible for damage to a variety of fruits and fruit trees. They also feed on the leaves of cucumber and other vine crops including peanuts, the squashes (Curcurbita) and melons (Cucumis and Citrullas). The larvae of several species are notorious for their damage to corn crops. The northern corn rootworm (NCR), D. longicornis barberi Smith and Lawrence, for instance, is an important corn pest in the upper Mississippi Valley region. The western corn rootworm (WCR), D. virgifera virgifera LeConte, and the Mexican corn rootworm (MCR), D. virgifera zeae Krysan and Smith, are significant pests in the midwestern and southcentral regions of the United States, respectively.
Another group of diabroticites associated with extensive feeding damage and implicated as vectors of a number of plant diseases is D. undecimpunctata. The southern corn rootworm (SCR), D. u. howardi Barber, commonly known in the adult stage as the spotted cucumber beetle, ranges east of the Rockies from southern Canada into Mexico. Larvae of the SCR are most damaging to corn in the southeastern U.S. where those hatched from eggs of overwintering adults either feed on seedling corn roots or bore into the base of the stem. They also cause widespread damage to peanut crops by penetrating the developing peanut, either consuming it or providing entry for pathogenic microorganisms. The larvae attack most other legumes and are also a significant pest of the cucurbits. Adults have been collected from some 280 species of plants, but are of primary concern on cucurbits and peanuts. The western spotted cucumber beetle (WSCB), D. u. undecimpunctata Mannerheim is found in the far western United States and the upper Baja Peninsula. In the Pacific Northwest, it has been known to cause severe damage to forage crops. Another diabroticite closely related to the SCR and the WSCB is D. u. duodecimnotata Harold indigenous to Mexico.
The continued search for alternatives to the widespread application of insecticides has led to the investigation of sex attractants as potential agents for use in integrated pest management. A number of economically important insects are currently monitored, partially controlled, or completely controlled by use of their own specfic sex pheromone. In the case of Diabrotica, application of this technology awaits identification and availability of the pheromones.
2. Description of the Prior Art
The production of a natural sex attractant by a species of Diabrotica was recognized by Cuthbert, Jr., et al. (J. Econ. Entomol. 57: 247-250 (1964)). Female abdomen alcohol extracts (10 female equivalents) of the banded cucumber beetle, D. balteata LeConte, were reported to lure males of this species from distances as far as 49 ft. (15 m.).
In an unpublished Ph.D. thesis (University of Nebraska, Lincoln (1968)), Cates was able to show that for the WCR a mating or copulation stimulant was produced by 6-day-old virgin females, but he could not conclusively demonstrate the presence of a sex attractant. Subsequently, Ball et al. (J. Econ. Entomol. 66: 1051-1053 (1973)) reported that hexane extracts from field-collected WCR females were attractive to WCR males under field conditions. Guss et al. (J. Chem. Ecol. 8: 545-555 (1982) and U.S. patent application Ser. No. 408,569) succeeded in both identifying and synthesizing the WCR sex pheromone. The active compound, 8-methyl-2-decanol propanoate (8-M-2-DP) has proven to be an effective attractant for adult males of the WCR, NCR, and the MCR, but it does not elicit a response from the SCR. However, a report by Branson et al. (Ann. Entomol. Soc. Amer. 71: 165-166 (1978)) that males of D. u. duodecimnotata in Mexico are attracted to traps baited with unfractionated volatiles from female SCR originating in South Dakota suggests the existence of a pheromone specific to the D. u. species.